As modern vehicles have diversified and become more sophisticated, data communications have increased between loads, such as electric and electronic equipments, mounted therein. Particularly, technology constituting a physical network using optical communication lines, such as optical fibers and the like, have been developed for carrying out a speedy and stable data communication, such that it is necessary to further simplify the physical network.
However, there is a drawback in that an increase of communication loads gives rise to structural complexity of multiplex devices, which in turn increases the physical size of multiplex devices in accordance with an increase of electronic equipment systems in need of control. This decreases the efficiency of the multiplex devices in optical communications.